While there’s no offline version of the installation, you should be able to accomplish this with a few extra steps.
The .rpt Inspector Online Broker installation will download and install the SAP Crystal Reports .NET Runtime 32bit (as of this post, version 13.0.23) and the Microsoft .NET Framework (as of this post, version 4.7.2) if these are not found on your system already.
So if you download these minimum versions directly (they have offline installers) and install them first, when you go to install the .rpt Inspector Online Broker it won’t try to download and install those dependencies first and simply install itself.